Observations of simultaneous coronal loop shrinkage and expansion during the decay phase of a solar flare

Khan, J. I.; Fletcher, L.; Nitta, N.

doi:10.1051/0004-6361:20054604

Cited by 9 publications

(8 citation statements)

References 33 publications

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“…The author reported that HXR sources (14 − 23 keV) were observed for about 50 minutes after flare maximum. The HXR source existing more than 1 hour after flare maximum was also reported by Khan et al (2006). In all these cases the HXR emission was observed close to and above the SXR emission source.…”

supporting

confidence: 74%

RHESSI Investigation of X-Ray Coronal Sources During Decay Phase of Solar Flares: I. Observations

Mrozek,

Koltun,

Kolomanski

et al. 2011

Preprint

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We analyse the observational characteristics for a set of Long Duration Events (LDE) using Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Excellent energy resolution (1 keV) of HXR images reconstructed with RHESSI allowed us to perform imaging spectroscopy of coronal loop top sources (LTS) observed for hours after maximum of the flare. We found that the sources are large structures. The diameter of an LTS is changing with time and energy. High temperature component can be observed for few dozen hours after the maximum. For some time intervals clear non-thermal component was observed in spectra, but there was no significant footpoint emission at that time. All thermal and non-thermal emissions originate from the LTS. The obtained observational characteristics were used in calculating the energy balance within LTS, which are presented in Kołomański et al. (2011)(this issue).

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supporting

confidence: 74%

RHESSI Investigation of X-Ray Coronal Sources During Decay Phase of Solar Flares: I. Observations

Mrozek,

Koltun,

Kolomanski

et al. 2011

Preprint

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“…Observations of inward moving waves do not necessarily support the idea of implosion. Inward moving waves, together with outward moving waves, may be produced by the reconnection event (Khan et al 2006).…”

Section: Discussionmentioning

confidence: 99%

Coronal hydromagnetic implosions

Janse

Low

2007

A&A

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Aims. The released magnetic energy in coronal events, i.e. in flares and coronal mass ejections (CMEs), is believed to have been stored locally in the coronal magnetic field. The energy in a magnetic field B is distributed in space with densitythat is also the isotropic magnetic pressure at each point in space. A localized release of magnetic energy would therefore imply a localized reduction of magnetic pressure. Hence, such a release could lead to an implosion of the magnetic structure as its atmospheric surrounding pushes inward. Whether an implosion would take place immediately depends on how fast the released energy can escape, through optically-thin radiation, thermal conduction, hydromagnetic waves, and, the magnetic channeling of high-energy particles. Methods. We determined whether an expansion or an implosion would occur when cylindrical tubes of twisted flux relaxed to lower energy states. Depending on the dynamical nature of the relaxation we assumed, relevant dynamical invariants were invoked to relate a particular end state to the given initial state. Results. Comparing the initial and the end state, we found that when most of the liberated energy escaped the cylinder imploded. The results suggest that implosions may take place simultaneously with flares and CMEs.

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“…This flare has a variety of interesting phenomena, some of which have been examined and reported elsewhere (Khan et al 2000;Klassen et al 2001;Hudson et al 2003;Khan et al 2006). In particular, Khan et al (2006) found simultaneous retracting and expanding soft X-ray emitting coronal loops above the main flaring arcade during the decay phase of the flare. The supra-arcade downflows appeared shortly after these moving loops.…”

Section: Downflows Starting During the Flare Decay Phasementioning

confidence: 91%

“…Recently, Khan et al (2006) reported observations of simultaneous retracting and expanding distinct coronal loops observed in emission in soft X-rays during a solar flare. For the particular event they examined, there were also supra-arcade downflows and these were clearly observed to start during the decay phase of the flare.…”

Section: Introductionmentioning

confidence: 99%

The relative timing of supra-arcade downflows in solar flares

Khan¹,

Bain²,

Fletcher³

2007

A&A

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Context. Supra-arcade downflows (generally dark, sunward-propagating features located above the bright arcade of loops in some solar flares) have been reported mostly during the decay phase, although some have also been reported during the rise phase of solar flares. Aims. We investigate, from a statistical point of view, the timing of supra-arcade downflows during the solar flare process, and thus determine the possible relation of supra-arcade downflows to the primary or secondary energy release in a flare. Methods. Yohkoh Soft X-ray Telescope (SXT) imaging data are examined to produce a list of supra-arcade downflow candidates. In many of our events supra-arcade downflows are not directly observed. However, the events do show laterally moving (or "waving") bright rays in the supra-arcade fan of coronal rays which we interpret as due to dark supra-arcade downflows. The events are analysed in detail to determine whether the supra-arcade downflows (or the proxy waving coronal rays) occur during a) the rise and/or decay phases of the soft X-ray flare and b) the flare hard X-ray bursts. It is also investigated whether the supra-arcade downflows events show prior eruptive signatures as seen in SXT, other space-based coronal data, or reported in ground-based Hα images. Results. A substantial majority of supra-arcade downflow events show downflows which start during the soft X-ray flare rise phase (73%), occur during hard X-ray bursts (90%), and have prior eruptive signatures associated with them (73%). However, we find a single event (2% of the total) which clearly and unambiguously showed supra-arcade downflows starting during the soft X-ray flare decay phase. Conclusions. Since the majority of supra-arcade downflows occur during the rise phase of the soft X-ray flare and the time of hard X-ray bursts, and have prior eruptive signatures this suggests that they are related to the main flare energy release process. Furthermore, the suggested association of supra-arcade downflows with recently reconnected magnetic field lines means they may indeed be considered as evidence for a magnetic reconnection process. The single supra-arcade downflow event which unambiguously started during the decay phase of the flare occurred during hard X-ray bursts and thus appears to be related to late energy release.

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Observations of simultaneous coronal loop shrinkage and expansion during the decay phase of a solar flare

Cited by 9 publications

References 33 publications

RHESSI Investigation of X-Ray Coronal Sources During Decay Phase of Solar Flares: I. Observations

RHESSI Investigation of X-Ray Coronal Sources During Decay Phase of Solar Flares: I. Observations

Coronal hydromagnetic implosions

The relative timing of supra-arcade downflows in solar flares

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